This is purely anecdotal however I've been doing Rails dev (and prior to that Javascript, PHP and even Matlab) for 14 years and I have only a vague grasp how mo

This is purely anecdotal however I've been doing Rails dev (and prior to that Javascript, PHP and even Matlab) for 14 years and I have only a vague grasp how most of that list works. That's not because I'm lazy or scared or even disinterested. I've exhaustively learned everything about anything that what I do involves and how most of what it touches works as well. However the simple truth for me has been that I've never worked on things that needed to know about the things you're talking about. I constantly do need to know more about the fundamentals of the systems I actually work with - Rails, Angular, HTML, caching, Node etc. I'm sure there will come a point when I need to know more about some of those things too. However there is a tonne that I don't know even about the things that I need to know about and I will always invest my time in learning those things. That's why I would always focus interviews on the languages and frameworks that someone actually uses. Those may be the ones you describe but for plenty of developers may well not.